import math
x,y,x2,y2 = map(float, raw_input().split())
print '%.7f' % math.sqrt((x-x2)**2 + (y-y2)**2)  import math math x,y,x2,y2 = map(float, raw_input().split()) x map(float, raw_input().split()) map float raw_input().split() ().split () raw_input split y x2 y2 print '%.7f' % math.sqrt((x-x2)**2 + (y-y2)**2) '%.7f' math.sqrt((x-x2)**2 + (y-y2)**2) math.sqrt math sqrt (x-x2)**2 + (y-y2)**2 (x-x2)**2 x-x2 x x2 2 (y-y2)**2 y-y2 y y2 2 x,y,x2,y2 = map(float, raw_input().split()) map(float, raw_input().split()) x y,x2,y2 = map(float, raw_input().split()) map(float, raw_input().split()) y y2 = map(float, raw_input().split()) map(float, raw_input().split()) y2 x2,y2 = map(float, raw_input().split()) map(float, raw_input().split()) x2
import math
x,y,x2,y2 = map(float, raw_input().split())
print '%.7f' % math.sqrt((x-x2)**2 + (y-y2)**2) 